Large machines such as, for example, wheel loaders, off-highway haul trucks, excavators, motor graders, and other types of earth-moving machines include frames to support their movement. Some of these frames are weld reparable (the frames are expected to crack during their economically useful life). Cracks in the frame are detected during regular inspections, and then repaired through welding. But, because of the size of the machines and/or the working environment of the machines, the frames can be difficult to inspect quickly and efficiently. In fact, it is not uncommon for a machine to be taken out of service for twenty-four hours while its frame is first completely cleaned, and then visually inspected for cracks. This problem can be exacerbated when parts of the frame are not easily accessible to maintenance crews. A frame that requires regular complete visual inspections can result in low productivity and efficiency. Also, potentially hazardous cracks may not be detected through a visual process. For example, a crack may form in a hidden side of a frame element. After an inspection, the crack may expand until it completely severs the frame element. When the frame element is severed, a portion of the machine may collapse, causing injury to an operator or nearby person, or extensive damage to the machine itself or a nearby machine or structure.
One way to reduce inspection time associated with crack detection is described in U.S. Pat. No. 4,721,413 (the '413 patent) issued to Crohas et al. on Jan. 26, 1988. The '413 patent describes a marine platform with a structure consisting of a lattice of tubular elements sealingly connected to one another. When a crack forms in one of the tubular elements, a fluid passes into and/or out of the tubular element. Some of the tubular elements are submerged, and have attached pickups. Each pickup is configured to detect the passage of fluid into and/or out of a tubular element. The interiors of multiple tubular elements may be connected to each other, thereby increasing the detection region of a pickup. When a pickup detects fluid passage, the pickup acoustically transmits a signal to a submerged intermediate transmission means, which wiredly transmits the signal to an unsubmerged signal acquisition unit. The signal contains information about where the pickup is located and what the pickup detected.
Although the pickups of the '413 patent may help detect cracks in a tubular structure, the pickups may do little to pinpoint the exact location of a crack. Furthermore, though the pickups of the '413 patent may communicate the general region of the crack to a signal acquisition unit, the signal acquisition unit may do little to assess the tolerability or criticality of the crack. In addition, though the pickups of the '413 patent may detect the existence of the crack during the time period between inspections, permanent installation of pickups may be prohibitively expensive for certain applications.
The disclosed method and system are directed to overcoming one or more of the problems set forth above.